We refer to a farming system as “diversified” when it intentionally includes functional biodiversity at multiple spatial and/or temporal scales, through practices developed via traditional and/or agroecological scientific knowledge. Farmers manage this functional biodiversity to generate critical ecosystem services to agriculture . At the plot scale, diversified farming systems may include multiple genetic varieties of a given crop and/or multiple crops grown together as polycultures, and may stimulate biodiversity within the soil through addition of compost or manure . By crops, we mean either annual or perennial crops, including tree crops. At the field scale, DFS may include polycultures, non-crop plantings such as insectary strips, integration of livestock or fish with crops , and/or rotation of crops or livestock over time, including cover cropping and rotational grazing. Around the field, DFS may incorporate non-crop plantings on field borders such as living fences and hedgerows. At the landscape scale, DFS may include natural or semi-natural communities of plants and animals within the cropped landscape/region,4x8ft rolling benches such as fallow fields, riparian buffers, pastures, meadows, woodlots, ponds, marshes, streams, rivers, and lakes, or combinations thereof . The resulting heterogeneous landscapes support both desired components of biodiversity and “associated biodiversity”; together these two elements make up agrobiodiversity .
Components of the agrobiodiversity within DFS interact with one another and/or the physical environment to supply critical ecosystem services to the farming process, such as soil building, nitrogen fixation, nutrient cycling, water infiltration, pest or disease suppression, and pollination, thereby achieving a more sustainable form of agriculture that relies primarily upon inputs generated and regenerated within the agroecosystem, rather than primarily on external, often nonrenewable, inputs . Spatial considerations are important, since different components of the system must be in sufficient proximity, at each relevant scale, to create needed interactions and synergies. For example, the utility of intercropping for reducing below ground soil disease depends on spacing the different crops such that their root systems interact . Similarly, wild bee communities can only provide complete crop pollination services when a sufficient proportion of their natural habitat occurs within a given distance of crop fields . A DFS is not only spatially heterogeneous, but is variable across time, due both to human actions , and natural successional processes. Figure 1 presents the conceptual model of a DFS. The term agroecology goes back more than 80 years and originally referred to the ecological study of agricultural systems . Much agroecological work seeks to bring Western scientific knowledge into respectful dialogue with the local and indigenous knowledge that farmers use in managing ecological processes in existing agroecosystems . More recently this hybrid science has evolved to include the social and economic dimensions of food systems .
Partly in response to the industrialized agriculture of the Green Revolution , agroecology also came to mean the adoption of sustainable agricultural practices , and became an integral component of various social movements seeking alternatives to industrial agri-food systems. Thus agroecology currently holds multiple meanings, and can refer to an inter- or transdisciplinary science, a set of sustainable farming practices, and/or a social movement . DFS is not an alternative to agroecology. Rather, DFS is a framework that draws from agroecological, social, and conservation sciences to focus analytical and action-oriented attention toward farming systems in which cross-scale ecological diversification is a major mechanism for generating and regenerating ecosystem services and supplying critical inputs to farming. Agroecological principles and methods can be used to evaluate DFS and to design or revive processes of diversification . In this essay and series of articles, we explore the ramifications of DFS for both ecological health and socioeconomic welfare, as well as examining the intersection of DFS with existing industrialized agricultural systems, supply chains, and national and international policies. DFS are complex social-ecological systems that enable ecological diversification through the social institutions, practices, and governance processes that collectively manage food production and biodiversity . As many political ecology scholars emphasize, ecosystems are densely interconnected with social relationships . Ecological variables such as soil, water, and habitat help configure an array of farming practices, exchanges of food and resources, and landscape management decisions that, in turn, influence the structure and function of the ecosystem. Further, as ecosystem services are generated and regenerated within a DFS, the resulting social benefits in turn support the maintenance of the DFS, enhancing its ability to provision these services sustainably . This interplay underlies numerous historically occurring and emerging DFS worldwide. Conversely, socio-political and economic processes such as the decrease of access and control over seeds or increased dependence on commodity markets can intervene to disrupt such feedback cycles, thus weakening DFS. The industrialization of agriculture has led to growing homogeneity across food systems as farming techniques and markets become more standardized .
As a consequence, the complex social relationships underlying agriculture and ecosystem service provision have become less visible. Focusing on DFS can help farming communities, researchers, policy makers, and industry recognize and restore these relationships. At their core, DFS depend on agroecological principles that are developed in and through the social relationships among working farmers, their communities and environments, and researchers, including ecologists, anthropologists, agronomists, and ethnobiologists . As seen in the Kreman et al. examples these principles take varied forms depending on local conditions. To understand how DFS may develop, function, and evolve over time and space, the particular context of each DFS needs to be studied, paying particular attention to the politics and power relations that reciprocally shape its ecological conditions. Many DFS were developed through traditional and indigenous farming knowledge and agrobiodiversity that was accumulated over millennia . More recently, other DFS have been created through targeted agroecological studies designed by scientists to solve particular problems . Historically, much knowledge about biologically diverse farming practices has been created and shared through peer-to-peer learning within traditional farming communities and, more recently, also through their collaboration with researchers interested in further developing agroecology . These relationships continue to be critical to the growth of DFS in new societal contexts and geographic locations. Since the 1980s, with the rise of the Campesino-a-Campesino and La Via Campesina movements, institutions such as government agencies, domestic and international NGOs, and universities have become increasingly active in promoting and diffusing agroecological principles through research networks and programs . These actors have added new institutional dimensions to the social relationships that help sustain DFS. An illustration of how social and ecological systems interpenetrate within DFS is in the Andean highlands, where indigenous farmers have managed their lands agroecologically for 3,000 years . The ongoing interplay between human management and physical ecology has created a landscape of agroclimatic belts at different altitudes, each characterized by specific field rotation practices, terraces, and irrigation systems, and the selection of specific animals, crops, and crop varieties . Within these belts, traditional knowledge has helped sustain tremendous genetic diversity, by perpetuating adapted land races and wild relatives of crops. Social cooperation is essential to managing the verticality and heterogeneity of the Andean ecosystem. A barter economy based on reciprocity, for example, facilitated complementary exchanges of plants and animals between ecological zones along the steep elevation gradient . In industrialized systems in both developed and developing countries, farmers must now negotiate with corporate food buyers, buy agrochemical and seed inputs from agents, seek loans from bank officials, and work with agricultural extension experts trained in pesticide use. Farmers rely on such relationships to compete effectively in supply chains and to manage changing ecological conditions, such as pest outbreaks. Nonetheless, these particular types of relationships often push individual farms to increased dependence on banks, damaging livelihoods, and undermining collaborative social learning groups as farmers specialize in a single crop and maximize short-term yields through the use of external inputs, to meet loan repayments.
The economic pressures in these tightly linked systems generally corrode ecosystem services, which are the very foundation of support for potential DFS. Farmers in industrialized systems may also engage in exploitative relations with immigrant or impoverished laborers, paying inadequate wages and enforcing long hours,flood and drain table helping perpetuate the apparent cheapness of food. Industrial production creates a number of “distances” between producers and consumers such that information flow diminishes across the supply chain . Thus within the industrial agri-food system, consumers remain relatively ignorant about the conditions of production, and would be less able to choose between products based on sustainability criteria, if they value these, and to exercise their buying power in favor of DFS. In turn, the risk perceptions of consumers and corporations may inhibit the growth of DFS. For example, during the recent food safety scare in fresh leafy vegetables in California, corporate buyers insisted that growers remove native vegetation bordering fields that might attract wildlife. This action was taken largely to assuage consumer concerns, despite the lack of scientific support . In alternative agricultural systems such as organic or low-input farming, farmers can build particular forms of relationships that help sustain ecosystem services and social infrastructure more effectively. We discuss many of these relationships, including direct marketing, fair trade certification, and food justice movements. In developing and studying these alternative systems, however, researchers, policy makers, and NGOs often neglect race, socioeconomic, and gender issues, or sublimate them into a broad social justice category. Finding ways to be far more inclusive of diverse racial, gender, and socioeconomic groups can help strengthen the socialecological basis of agriculture. For instance, African-American growers once represented a sizable proportion of the U. S. farmer population, or one million in 1910, declining to 18,400 by 1997, due to race discrimination and violence, lack of land tenure , and multiple waves of economic migration from the South to urban centers . Many of these black farmers used DFS practices; their displacement helped create an opening for industrialized monocultures. Now, many new farmers in rural and urban areas are black, Latino, or Asian; there is evidence that these farmers are more likely than their established peers to embrace sustainable agriculture practices if adequately supported . Immigrants such as the Hmong may sometimes develop culturally relevant, more diversified food production enclaves within industrialized systems that preserve their traditions and provide livelihoods.They are developing new linkages between cities and nearby rural areas, potentially helping recreate DFS. For example, Will Allen founded Growing Power, an urban farming NGO that serves disadvantaged neighborhoods in Milwaukee and Chicago, attempting to encourage youth of all races to take up diversified farming. In Chicago, black activists and physicians have formed the Healthy Food Hub, a food aggregation NGO which sources produce from a historically black farming community, Pembroke Township, about an hour from Chicago. These efforts show how people can demand greater political agency in building a democratic DFS . New quantitative and qualitative research is badly needed to evaluate and critique the social benefits that DFS may provide in contrast to industrialized systems. In general, further analysis is needed to understand how the social elements of DFS can help generate and regenerate ecosystem services, thus maintaining diversified farming systems. In turn, more research is required on the political and socioeconomic interventions that could help rebuild or sustain the socialecological cycles that underlie DFS.DFS are often embedded in social, political, and economic conditions that differ from those accompanying industrialized monocultures , particularly with respect to core stakeholders, markets, and distribution systems. Yet, DFS may not always be able to realize their potential social-ecological benefits due to the lack of enabling environments. We explore how alternative agri-food networks and social movements relate to DFS and assess their potential to both maximize social benefits and promote DFS through their demands for food sovereignty and food justice. The agri-food systems approach reveals the interconnected systems of inputs, labor, land, capital, governance and knowledge that maintain specific types of agricultural production, distribution, and consumption systems . The governance and structure of the food system upstream from the farm, such as international agricultural trade liberalization policies that promote cheap food imports from industrial into developing countries, government subsidies for fossil fuel-based agrochemicals and commodity crops and irrigation projects that primarily benefit larger landholders , all help to maintain the industrialized agri-food system .